containing the genera Discorbites, Siderolites, Polystomella,
Vorticialis, Nummulites, Nautilus. To these may be added Simplegas and
Endosiphonites. Fig. 472 to 476.
NAUTILUS. Auct. (_A little boat._) _Fam._ Nautilacea, Lam. and
Bl.--_Descr._ Convolute, discoid, chambered, symmetrical; spire partly
or entirely concealed by the last whorl; aperture modified by the last
whorl, wide, sinuated on the dorsal margin; interior surface pearly;
septa dividing the chambers simple; siphon discontinuous.--_Obs._ The
shell named Nautilus by Pliny is the Argonauta of modern authors, a
thin shell, not chambered. The Nautili are known from the Ammonites by
the septa being simple, not sinuated as in the latter genus, and in
general the volutions of the spire are not visible. Three or four
species are known inhabitants of the Pacific Ocean and Australian
Ocean. The fossil species are found in the tertiary, and also in the
secondary strata, as low down as the Mountain limestone. N. pompilius,
Frontispiece.
NAYADES. Lam. A family of the order Conchifera Dimyaria, Lam. described
as containing fresh-water bivalve shells, with or without teeth on the
hinge. They are all pearly within, and have a thick, rather smooth
epidermis without. This family contains a great variety of shells,
which have been separated into an immense number of genera, but which
G. B. Sowerby, sen. gives very good reasons for uniting under one
generic name. The most generally received distinctions are as follows:
1. CASTALIA. Two cardinal, one lateral, ribbed teeth. This genus is
removed from the family of Trigonacea. Fig. 140.
2. UNIO. Teeth various. Fig. 142, 145, 149, 148, 147, 151, 141.
3. HYRIA. Trigonal, alated. Fig. 143, 150.
4. ANODON. No teeth. Fig. 152.
5. IRIDINA. Hinge crenated. Fig. 150.
NECTOPODA. Bl. The first family Nucleobranchiata, Bl. containing the
genera Carinaria and Firola; the latter is not a shell.
NEMATOPODA. Bl. The first class of the sub-type Malentozoa, Bl.
containing all the mollusca with multivalve shells, except Chiton, and
divided into the families Lepadicea and Balanidea, corresponding with
Lamarck's sessile and pedunculated Cirripedes, and with the Linnæan
genus Lepas.
NEMATURA. Benson. _Fam._ Turbinacea, Lam.--_Descr._ Thin, nearly oval,
somewhat compressed from back to front; spire acute, consisting of few
rounded whorls; last whorl large, but contracted near the aperture;
aperture small, oblique, rounded anteriorly; peritreme continuous,
thin; operculum spiral, horny, with few volutions.--_Obs._ The
distinguishing character of this genus is the contraction of the last
whorl near the aperture, in which respect it is nearly resembled by the
shell called Cyclostoma lucidum. Two recent and one fossil species, all
very minute, are described by Sowerby in Loudon's Magazine of Natural
History, New Series. Fig. 305.
NERINEA. Defr. _Fam._ Canalifera, Lam.--_Descr._ Turrited, oblong,
sub-canaliculated, consisting of numerous whorls; aperture with a
strong fold on the columella, one on the outer lip, and one on the
inner lip at the edge of the body whorl.--_Obs._ This genus is only
found in a fossil state usually in the Oolitic beds, it is not
resembled by any other; the strong, prominent folds on the three upper
angles of the subquadrate aperture present a singular appearance in a
section. One species has been named N. Hieroglyphus. We give N.
Goodhallii, fig. 374.
NERITA. Auct. _Fam._ Neritacea, Lam. Hemicyclostomata, Bl.--_Descr._
Smooth or ribbed, semiglobose; spire short, sometimes flat, consisting
of few volutions; aperture large, semilunar; outer lip thick, entire;
inner lip thickened, dentated at the edge, spread over the body whorl,
forming a flattened disc; operculum shelly, spiral, with an appendage
by which it is locked under the sharp edge of the columella.--_Obs._
These marine shells are known from Neritina by the thickness of the
shell and the want of the thick, horny, dark coloured epidermis; from
Natica by the flat area produced by the spreading of the thickened
columellar lip. N. Peloronta, fig. 330. N. polita, fig. 329.
NERITACEA. Lam. A family of the first order of Trachelipoda, Lam.
containing the following genera:
1. NAVICELLA. Apex terminal, not spiral; inner lip septiform. Fig.
323.
2. NERITA. Columellar lip septiform, edge with distinct teeth;
shell thick. Fig. 330.
3. NERITINA. Shell thin; columellar lip septiform, edge
denticulated; generally a thick, dark coloured epidermis. Fig. 324
to 326.
4. NATICA. Having an umbilicus behind the columellar lip, with a
spiral callosity. Fig. 327, 328.
5. NERITOPSIS. Edge of the columellar lip with a deep notch. Fig.
331.
6. PILEOLUS. Patelliform; apex central; columellar lip septiform,
leaving the aperture small. Fig. 332.
7. JANTHINA. Columellar lip linear; aperture angulated. Fig. 333.
NERITINA. Lam. _Fam._ Neritacea, Lam.--_Descr._ Thin, semiglobose,
obliquely oval, smooth, flattish in front; spire short, sometimes
depressed, consisting of few rapidly increasing whorls; aperture
semicircular; outer lip thin, sharp; columellar lip broad, flat, its
inner edge straight, denticulated; operculum testaceous, semicircular,
sub-spiral, with an articulating process on the inner edge.--_Obs._
This genus of fresh-water shells differs from Nerita in the minuteness
of the denticulation of the columella, as well as in the characters
mentioned in our observations upon the latter genus. N. spinosa,
(Clithon, Montf.) fig. 325. N. virginea, fig. 324. N. perversa, Lam.
(Velates, Montf.) fig. 326. All the species known up to the present
time, with the exception of three, are represented in the author's
Conchological Illustrations, parts 86, 87, 90, 91, 94 to 100. The
catalogue accompanying these representations enumerates 59 species.
NERITOPSIS. Gray. _Fam._ Neritacea, Lam.--_Descr._ Sub-globose, thick,
cancellated; spire short, composed of few rapidly increasing whorls;
aperture transverse, sub-orbicular; outer lip thickened within;
columellar lip thick, rather flat, with a large rounded notch in the
centre of its inner edge.--_Obs._ This genus most nearly resembles
Nerita, from which it differs in the peculiar notch of the columella.
N. granosa, fig. 331.
NICANIA. Leach. ASTARTE, Sowerby. The same as CRASSINA of Lamarck.
NITIDELLA. Sw. A genus of "Columbellinæ," Sw. thus described:
"Bucciniform, small, ovate, smooth, glassy; aperture effuse; outer lip
slightly thickened, faintly inflexed, and generally striated
internally; inner lip somewhat flattened above; base of the pillar with
one or two slight internal folds, or a single angular projection.
Columbella nitida, _Lam._ (fig. 17, _c._ p. 151.)" Sw. p. 313.
NOBIA. Leach. _Order_, Sessile Cirripedes, Lam. This genus resembles
Pyrgoma, Auct. consisting of a conical paries, supported upon a
funnel-shaped cavity in the madrepore, but differs in its operculum,
which consists of two valves, whereas that of Pyrgoma has four. N.
grandis, fig. 29.
NODOSARIA. Lam. and ORTHOCERA have been united by Sowerby under the
name of the first. _Fam._ Orthocerata, Lam. and Bl.--_Descr._ Straight,
chambered, elongated; chambers more or less ventricose; septa
perforated by a central siphon.--_Obs._ This genus consists only of
fossils found in sub-appenine tertiary beds. It is placed by De
Blainville in one of his divisions of the genus Orthoceras, which is
characterized as "species not striated, and with chambers very much
inflated." N. æqualis, fig. 465.
NODOSE. Having tubercles or knobs.
NOGROBS. Montf. A fossil appearing from the figure and description to
resemble Belemnites.
NONION. Montf. A genus of microscopic Foraminifera.
NONIONINA. D'Orb. A genus of microscopic Foraminifera.
NOTREMA. Rafinesque. A shell described as composed of three integral
valves, concerning which De Blainville puts the query, "ne seroit-ce
pas plutôt une Balanide mal observée?"
NOVACULINA. Benson. (_Novacula_, a razor.) _Fam._ Solenacea,
Lam.--_Descr._ Equivalve, inequilateral, transversely elongated;
external ligament communicating with the interior of the shell by an
oblique channel; beaks prominent; hinge line nearly straight, with one
narrow curved cardinal tooth in one valve, entering between two similar
teeth in the other; siphonal scar long; extremities of the shell
gaping; epidermis thin, light brown, folding over the edges and
connecting the dorsal margins. _Hab._ Jumna, Gooti, and Ganges. Fig.
63.
NUCLEOBRANCHIATA. Bl. The fifth order of the second section of
Paracephalophora Monoica, Bl. the shells of which are described as
symmetrical, more or less curved, or longitudinally rolled up and very
thin. This order contains, _Fam._ 1. Nectopoda, containing Carinaria;
_Fam._ 2. Pteropoda, containing Atlanta, Spiratella and Argonauta.
NUCLEUS. (_A kernel._) Anything forming a centre around which matter is
gathered. The nucleus of shells is the first formed part; the first
deposit of shelly matter to which the successive layers are added; the
apex of the spiral cone, of which most shells are composed. (See CONE.)
The nucleus is formed within the egg in oviparous, and within the old
shell in viviparous mollusca. It is frequently more transparent and
light than the remainder of the shell, and sometimes falls off; when
this occurs the shell is said to be decollated.
NUCULA. Lam. (_A small nut._) _Fam._ Arcacea, Bl. and Lam.--_Descr._
Equivalve, inequilateral, transverse, covered with an epidermis; hinge
linear, with a series of sharp, angulated teeth, arranged in a line on
each side of the umbones, and a central ligamentary pit; muscular
impressions two, simple; palleal impressions not sinuated.--_Obs._ The
row of teeth on each side of the umbones, and the ligamentary pit in
the centre of the hinge prevent the pretty little shells of this genus
from being confounded with any other. Thirty-four figures are
enumerated in the catalogue by Sowerby, sen. which accompanies the
Conchological Illustrations of the author. The new species, to the
amount of 24, have been figured in parts 14 to 16, of the above
mentioned work. Recent Nuculæ are found from the frozen to the torrid
zones, and the fossil species occur in nearly all the beds from the
Pliocene to the Carboniferous system.
NUMMULACEA. Bl. The third family of Cellulacea, Bl. described as
containing shells or calcareous bodies, which are characterized as
discoidal, lenticular; without the slightest traces of whorls to be
seen externally. The whorls are numerous, internal, and divided into a
great number of cells, which are separated from each other by
imperforate septa. This family contains the genera Nummulites,
Siderolites, Vorticialis, Helicites, Orbiculina, Placentula.
NUMMULTTES. Lam. (_Nummus_, money.) _Fam._ Nautilacea, Lam.--_Descr._
Orbicular, convolute, shewing no trace of spire externally; interior
divided into cells spirally arranged.--_Obs._ The singular fossils
composing this genus receive their name from their external resemblance
to a battered coin. Fig. 472. N. lenticulina.
NUX. Humph. CYCLAS, Lam.
NYMPHACEA. Lam. A family belonging to the order Conchifera Dimyaria,
Lam. Ligament external, placed on a prominent fulcrum. This family
contains the following genera:
1. SANGUINOLARIA. Rostrated, gaping; two cardinal teeth in each
valve, including _Soletellina_ and _Lobaria_. Fig. 98, 99.
2. PSAMMOBIA. Quadrate; valves closed, including Psammotæa. Fig.
100.
3. CORBIS. Thick, fimbriated; a cardinal tooth in the centre of a
pit. Fig. 101.
4. GRATELOUPIA. A series of small teeth filling a triangular area.
Fig. 102.
5. EGERIA. One single and one double cardinal tooth. Fig. 103.
6. LUCINA. Rounded; anterior muscular impression tongue-shaped.
Fig. 104.
7. TELLINA. An anterior fold in the ventral margin; lateral teeth.
Fig. 105, 106.
8. TELLINIDES. No anterior fold; no lateral teeth. Fig. 107.
9. DONAX. Margin denticulated; shell wedge-shaped. Fig. 108.
10. CAPSA. Margin not denticulated, no lateral teeth. Fig. 109.
OBELISCUS. Humph. TROCHUS, Lam.
OBLIQUE. (_obliquus._ lat.) In a slanting direction. The whorls of
spiral univalves generally take an oblique direction in reference to
the imaginary axis of the shell. A bivalve is said to be oblique when
it slants off from the umbones. An example of this is seen in Avicula,
fig. 163.
OBSOLETE. (_obsoletus_, lat.) Worn out, out of use. This term is used
to express an indistinctness of character, which sometimes results from
the action of sea-water upon unprotected parts of the shell, and
sometimes from the deposits of enamel formed in age, and covering the
early striæ, ribs, teeth, &c. thereby rendering them less acute.
OBTUSE. (_obtusus_, blunt.) The application of this term is not
peculiar to conchology. It is most frequently used to express the
character of the spire. _Ex_. The apex of Megaspira, fig. 294.
OCEANUS. Montf. ("Corne d'ammon vivant," Fr.) NAUTILUS umbilicatus,
Auct.
OCTHOSIA. Ranz. CLITIA, Leach.
OCTOCERA. Bl. The first family of the order Cryptodibranchiata, Bl.
containing the genus Octopus. A species of which being found in the
Argonauta, or Paper Sailor, has given rise to the long continued
controversy as to whether it is really the constructor of the shell, or
whether it is a mere pirate, and having destroyed the true animal of
the Argonaut, has possessed itself of the habitation. This question is
now set at rest. See ARGONAUTA.
OCTOGONAL. (_octogonum._) Having eight angles. For an example, see
Dentalium, fig. 2.
OCTOMERIS. Sow. ([Greek: oktô], _octo_, eight; [Greek: meros], _meros_,
part.) _Fam._ Balanidea, Bl. _Order_, Sessile Cirripedes,
Lam.--_Descr._ Eight principal valves circularly arranged, forming a
compressed cone, attached by a jagged base; aperture enclosed by an
operculum, consisting of four valves in pairs.--_Obs._ The only genus
of Sessile Cirripedes agreeing with this in the number of principal
valves is Catophragmus, Sow. which is, however, sufficiently
distinguished by the several rows of smaller valves by which the
principals are surrounded at the base. O. angulosus, fig. 24.
ODONTIS. Sow. MONODONTA, Lam.
ODOSTOMIA. Flem. _Descr._ "Shell conical; aperture ovate; peristome
incomplete, retrally, and furnished with a tooth on the pillar." A
genus composed of several small species of land shells. Turbo plicatus,
Spiralis, Unidentatus, &c. Mont.
OLIVA. Auct. (_An olive._) _Fam._ Convoluta, Lam. Angyostomata.
Bl.--_Descr._ Oblong, cylindrical, thick, smooth, shining; spire very
short, with sutures distinct, aperture elongated, notched at both
extremities; outer lip generally thick; columella thick, obliquely
striated, terminated by a tumid, oblique, striated varix; a raised band
passing round the lower part of the body whorl.--_Obs._ The shells
composing this well known genus present a great variety of rich
markings and brilliant colours. They are marine and tropical. Fossil
species are found sparingly in the London Clay and Calcaire-grossièr.
The Ancillariæ are distinguished from this genus by the sutures of the
whorls being covered by enamel. O. maura, fig. 457.
OLIVELLA. Sw. A genus of "Olivinæ," Sw. thus described: "Oliviform;
spire (typically) rather produced; the tip acute; inner lip not
thickened; outer lip straight; base of the pillar curved inwards, and
marked by two strong plaits; upper plaits obsolete or wanting; aperture
effused at the base only; biplicata, Tank. Cat. 2332. purpurata. Zool.
Ill. ii. 58. f. 1. mutabilis. _Say._ eburnea. Zool. Ill. ii. 58, f. 2.
conoidalis. _Lam._ No. 57. oryza. _Lam._ No. 62."
OLYGYRA. Say. Mentioned by Ranz as properly belonging to Helicina. H.
neritella, Auct.
OMALAXIS. Desh. Subsequently BIFRONTIA. Desh. Fig. 354.
ONISCIA. Sow. (G. B.) _Fam._ Purpurifera, Lam. Entomostomata,
Bl.--_Descr._ Oblong, sub-ovate, slightly turbinated, cancellated;
spire short; aperture elongated; terminating anteriorly in a very
short, recurved canal; outer lip thickened, denticulated within; inner
lip spread over a portion of the body whorl, granulated.--_Obs._ The
granulated inner lip is the principal character by which this genus is
distinguished from Cassidaria. In Oniscia the canal is not so produced.
O. oniscus, fig. 409.
ONUSTUS. Humph. A genus proposed by Humphrey and adopted by Swainson
who describes it thus: "Shell trochiform; the surface irregular, and
often covered with extraneous bodies, cemented and incorporated with
the calcareous substance of the shell; the under part of the body whorl
flattened or concave, umbilicate. O. Solaris. Mart. 173. f. 1700, 1701.
Indicus. Ib. 172. f. 1697. 1698." It is probable, from the above
description, that Mr. Swainson intended to include Trochus agglutinans
of authors. (Genus Phorus, Montf.) Fig. 360.
OPERCULAR. Of, or belonging to, the operculum. A term applied to the
valves which compose the operculum of multivalve shells, as
distinguished from the parietal valves, or those which are arranged
circularly and form the body of the shell.
OPERCULINA. D'Orb. A genus of microscopic Foraminifera.
OPERCULUM. (_A cover or lid._) The plate or plates with which many
molluscous animals enclose the aperture of their shells, when retired
within them. The operculum is sometimes horny, as in Trochus;
testaceous or shelly, as in Turbo. It is spiral when from a central or
sub-central nucleus, the successive layers take a revolving direction,
as in Trochus. It is concentric or annular when the outside edge of
each layer entirely surrounds the preceding one. It is unguiculated,
when the laminæ are placed side by side, as in Purpura. The opercula of
multivalve shells are composed of two or four pieces, which are called
the opercular valves. The shelly or membranaceous plate with which some
of the animals enclose the aperture of their shells, during the wintry
part of the year, for the purpose of protecting them while in a torpid
state, and which they get rid of by dissolving the edges, when
preparing to emerge from their temporary retirement, must not be
considered as the operculum, as it does not belong to or form part of
either the animal or its shell, but is produced for the occasion by a
secretion of the animal, being deposited in a soft state and
subsequently hardening. It is called the epiphragm, and may easily be
distinguished from the true operculum by the texture, and by the
circumstance of their being soldered to the edge of the aperture. The
operculum, on the contrary, is moveable, and is always composed of a
series of successive layers, corresponding with the growth of the
shell.
OPIS. Defr. A genus described by De Blainville as consisting of species
of Trigonia which have the umbones sub-spiral, with a large, striated
tooth on the hinge. Opis cardissoides, Trigonia, Lam. Opis similis,
Sow. Min. Con. pl. 232. f. 2.
ORAL. (_Os_, _oris_, mouth.) Applied to that part of a shell which
corresponds with the mouth of the animal, but very seldom used in this
sense.
ORBICULA. Lam. (_Orbis_, an orb.) _Fam._ Brachiopoda, Lam.
Palliobranchiata, Bl.--_Descr._ Inequivalve, irregular, sub-orbicular,
compressed, attached by a fibrous substance passing through a fissure
near the centre of the lower valve; upper valve patelliform, with the
umbo central; muscular impressions four in each valve, semilunar. South
America and West Indies.--_Obs._ Discina, Lam. is an Orbicula. Crania
is known from this genus by having no fissure in the lower valve, but
being attached by its substance. Hipponyx has only two muscular
impressions in each valve. O. lævis, fig. 201.
ORBICULAR. (_Orbiculus_, a little orb.) Of a round or circular form.
ORBICULINA. Lam. A genus of microscopic Foraminifera.
ORBIS. Lea. A minute fossil, described as "orbicular, with flat
quadrate whorls and aperture square," in other respects resembling
Solarium. O. Rotella, fig. 355, 356.
ORBITINA. Risso. A genus said to be established upon the nuclei of two
land shells.
ORBULITES. Lam. A genus separated from Ammonites on account of the last
volution covering the spire. This is generally considered as
characterizing the Nautili, and distinguishing them from the Ammonites;
but there are so many gradations that it seems impossible to maintain
the distinction in this respect. Fig. 479, O. crassus, fig. 480, O.
discus.
OREAS. Montf. Part of CRISTELLARIA, Lam. A genus of microscopic
Foraminifera.
ORTHIS. Dalman. ([Greek: orthos], _orthos_, straight.) _Fam._
Brachiopoda, Lam. One of the generic divisions of Brachiopoda by
Dalman, thus described: "Hinge rectilinear, with umbones distant; the
larger valve with a transverse, basal, smooth area, with a triangular
pit." O. basalis, fig. 207.
ORTHOCERA. Lam. See NODOSARIA.
ORTHOCERATA. Lam. A family of Polythalamous Cephalopoda, Lam.
containing the following genera:--
1. CONULARIA. Conical, externally striated; no siphon. Fig. 469.
2. AMPLEXUS. Cylindrical; margins of the septa reflected. Fig. 463.
3. ORTHOCERATITES. Straight, gradually conical; septa simple;
siphon central. Fig. 464.
4. NODOSARIA. Divided externally into lobes. Fig. 465.
5. BELEMNITES. Straight, conical; septa simple; siphon lateral;
apex solid; internal cast, or nucleus, pyramidal, separable. Fig.
466 to 468.
6. CONILITES. Like Belemnites, but external shell thin at the apex.
Fig. 470.
ORTHOCERATA. Bl. The first family of Polythalamacea, Bl. containing the
genera Belemnites, Conularia, Conilites, Orthoceras and Baculites. De
Blainville remarks that the genera included in this family are all
fossils, and known very imperfectly, in consequence of the greater part
of the specimens being only casts.
ORTHOCERATITES. Auct. _Fam._ Orthocerata, Lam. and Bl.--_Descr._
Straight, conical, divided into numerous chambers by simple septa
perforated by a central siphon. O. annulata, fig. 464.
OSTEODESMA. Desh. PERIPLOMA, Schum.
OSTRACEA. (_Ostracées_, Lam.) A family belonging to the second section
of the order Conchifera Monomyaria, the shells of which are described
as irregular, foliaceous, sometimes papyraceous, with the ligament
wholly or partly interior. The principal difference between the
Ostracea and the Pectinides consists in the absence of the auricles and
the foliated structure of the shells, for, although the Spondylus has
ex-foliations or spines upon the external surface, the shell itself is
compact and firm. This family contains the genera Gryphæa, Ostrea,
Vulsella, Placuna, Anomia, which may be thus distinguished:--
1. PEDUM. Flat, turned up at the sides, an hiatus for the passage
of a byssus. A triangular disc on the hinge. Fig. 179.
2. OSTREA. Foliaceous, irregular, hinge on a small triangular disc.
Including Dendostrea, Ostræa, Exogyra, Gryphæa. Fig. 180 to 183.
3. PLACUNA. Two diverging ribs near the umbones. Fig. 184.
4. PLACUNANOMIA. The same, but attached by fibres passing through a
hole in one valve. Fig. 189 to 191.
5. ANOMIA. No costæ, attached by a bony substance passing through a
hole in one valve. Fig. 186 to 188.
6. VULSELLA. Tongue-shaped, a ligamentary pit on the hinge. Fig.
185.
7. MULLERIA. Doubtful. Fig. 192.
OSTRACEA. Bl. The first family of the order Lamellibranchiata, Bl.
containing the genera Anomia, Placuna, Harpax, Ostrea (including
Dendostrea, Sw.) Gryphæa. To these may be added Placunanomia, Brod. and
Mulleria.